The Open Pixel Project (OPP) is a collaboratively made pixel art asset pack for platform games, with over 2000 sprites and tiles. I initiated the project in 2013, and it grew out to a total of 34 participants who submitted their artworks and put it in the public domain, over the course of 5 years.
The full pack can be downloaded for free at Itch, OGA, and our website openpixelproject.com
Countless games and demos have been made using these free assets
Promo video:
The OPP triggered the publication of the DB32 palette, possibly the most famous pixel palette to date as it has become the default in many drawing applications such as Aseprite.
Review: